Notch announced there will be two kinds of dragons:
Red Dragon - A dragon which flies around and can land. They roam the overworld. Running into one is probably reason to be careful. There's no news on if they only spawn at night but I assume dragons fly around all day. These are supposedly planned to be included after the official release.
Ender Dragon - A black dragon of insurmountable power. There will only spawn one in the Ender world (now known as The End). It will stay in the air and scoop down to attack you, breaking any block in it's path in it's rampage. Beating one is supposed to be near-to-impossible without serious equipment, enchantments and potion buffs. It probably takes a group to beat one. It's unknown if there will only be one at a time, or if only one spawns once. I imagine there is some kind of reward. They are bigger than Red Dragons and will already be included in 1.9.
An Ender Dragon in action.On items:
There seem to be enchanted items which you improve by using a spell from the new spellbook. Enchanting spells are casted by spending level-up points you get when you grab enough experience spheres (the yellowish green blobs mobs drop on death). Enchanted items get a
blue name, indicating they are magic or uncommon items and get bonuses similar to hack-'n-slash games such as diablo, examples are:
Knockback I,
Smite II etc. Golden apples suddenly have a
purple name, which seems similar to epic items in games such as World of Warcraft, Tabula Rasa, Diablo 3, so perhaps this indicates the future may hold legendary or rare epic items.